Pressure signs

[motoxxx_ryder]

I finally got my 6.5 on saturday and hit the range on sunday, 123gr amax, 25.5-28.5 in .5 incriments of 8208xbr.

my question is, at 28.5 i had 0 pressure signs no bolt swipe no flattened primers (br4) nothing.

I jsut wanted to be sure the grendel had typical pressure signs, after loading for the 458 socom i learned some calibers have no real pressure signs while others have a rather large window.

(ill try to get some rifle pics up later)

[FW Conch]

I assume you are shooting an AR.

28.5, with your combination, shows "no" pressure signs in my bolt rifle ... However, it has a nice long throat. I don't touch the lands with the 123 until 2.34xx"coal, so the extra space in the case relieves a lot of pressure. :-)

[cory]

Physical markings can be very deceiving in the Grendel, at least until you're well beyond 52ksi. Monitoring your Velocities has been a much more accurate indicator of high pressure, at least in my experience.

In my 16" Grendel on the light side, I can often feel a difference in recoil when I get to max pressures.

[motoxxx_ryder]

Physical markings can be very deceiving in the Grendel, at least until you're well beyond 52ksi. Monitoring your Velocities has been a much more accurate indicator of high pressure, at least in my experience.

In my 16" Grendel on the light side, I can often feel a difference in recoil when I get to max pressures.

this is why im asking i know on the 458 when you see pressure signs youre already way past.

when you say monitoring velocities is a better mark, what is a good mark to shoot for in a 20inch with 8208 xbr?

And yes its an AR platform sorry.

[cory]

I really can't help you there man, sorry. I use CFE for the 123gr+ stuff and use 8208 for the lighter stuff.

If I recall correctly, from others posting, you can expect exceptional accuracy, but not a lot of velocity.

A particular mark isn't waht I was referring to when I suggested watching velocities. Starting at a lower charge working up you should see a trend in the increase in velocity per gr, once it deviates from the observed trend you know you're getting into higher pressures.

Generally you'll see a decrease in the velocity gained per gr right up until you see a velocity spike. The velocity spike is a good indicator that you're above 52ksi.

[motoxxx_ryder]

I really can't help you there man, sorry. I use CFE for the 123gr+ stuff and use 8208 for the lighter stuff.

If I recall correctly, from others posting, you can expect exceptional accuracy, but not a lot of velocity.

A particular mark isn't waht I was referring to when I suggested watching velocities. Starting at a lower charge working up you should see a trend in the increase in velocity per gr, once it deviates from the observed trend you know you're getting into higher pressures.

Generally you'll see a decrease in the velocity gained per gr right up until you see a velocity spike. The velocity spike is a good indicator that you're above 52ksi.

AH ok ill take the chrono out, and run some testing. thank you for the info. i did a half moa with 25.5 im going to chrono it and see how its looks on velocity. I was hoping to have a node at a higher node to play at some longer ranges and use the 25.5 for majority of my shooting.

Is the CFE temp sensitive? Living in vegas i can go from 110 to 60 overnight, tac about killed me blowing primers going from 60 to 100.

[cory]

The verdict is still out on CFE. However, I haven't seen any reports of blowing primers with CFE.

[LRRPF52]

A sound approach to hand loading as you determine your charge weight increments is to take 1% of usable case volume with that powder. With 8208, 28.5gr is usually the ceiling with a 123gr in a SAAMI chamber.

1% of 28.5gr is .25gr, so you can round up or down for your charge weight increments. In this case, I normally use .3gr increments and no larger.

You will be able to develop a trend line looking at velocity over a chrono or magneto if you have them. Primer signs might not show up until 67,000psi in some cases, with slight cratering, or they can start to show at as low as 50,000psi. It just depends a lot on the strength of the primer cup and how much pressure is applied to it over time. This is why referencing reloading data and checking your actual speeds on the chronograph will give you a much better idea of where you are at.

[motoxxx_ryder]

ill repeat 1 shot from 25.5 to 28.5 in .5 increments over chrono and map the trend. then ill go 28.8, 29, 29.2, 29.5, 29.7 3 each and see if i find a good load at the higher velocities and stop at either a good load or when the velocities break trends.

Thanks alot for the info i have been reloading for a while so i know to tread lightly.

[cory]

You're in unknown territory where you may very well hit your limit with the first charge you try or not at all, and you don't want to replow established territory. I've been in the same boat. The problem here is that there are a lot of variables in temp, humidity, sun light, setup of the chrono, and others that can affect your velocity data, making that pressure limit more difficult to spot.

There are 2 approaches I'll take here. Starting 1gr+ below a known safe charge. Either.... (I'll use your current charges as an example)

OCW Route
I'll back up from the first desired load to test (28.8gr) by .3gr and load 2 rounds at each of the 4 subsequent charges (28.5gr, 28.2gr, 27.9gr, & 27.6gr). I'd also do 5 loads at each of your desired test loads, for good measure in getting a good trendline.

or

Ladder Route
This is good if resources are limited or you're just working with an expensive (which is relative to the shooter) round. I'll load 1 charges every .3gr from 27.6gr to 29.7gr and I'll do a ladder test looking for a node while monitoring my rifle's response to the load and the velocity data. Then I'll come back and run an OCW, if I find a node worth exploring.

Either way this gives me known safe velocities to compare my new velocity data with, all acquired under the same variables.

Just food for thought. Hope this helps.

Added: As I've said I have no experience or knowledge of 8208 under 123gr Projectiles. I suggest you take LRRPF52's advise under serious consideration.

[LRRPF52]

ill repeat 1 shot from 25.5 to 28.5 in .5 increments over chrono and map the trend. then ill go 28.8, 29, 29.2, 29.5, 29.7 3 each and see if i find a good load at the higher velocities and stop at either a good load or when the velocities break trends.

Thanks alot for the info i have been reloading for a while so i know to tread lightly.

Please don't load those. 8208 is a pretty fast powder, and everyone that has tried going above 28.5gr has seen a spike in pressure. 28.5gr under a 123gr is really where you want to stop.

[Jakal]

I would load 27.0, 27.3, 27.6, 27.9, 28.2 and finally 28.5. You should come up with a low and high accuracy node. Go back and drop .2 of a grain from the low side and add .2 to the high side unless at max. So if 27.6 was the low and 28.0 the high, my next ladder would be. 27.4, 27.6, 27.8, 28.0 and then 28.2. Basically you run a linear track via all charge weights over the chronograph. This will show the ramp up in velocity while tuning for an accurate load. It usually takes me 2 to 3 charge ladders to find my load but during the process I have detailed alot of info and gain a better understanding of what my rifle likes.

I then start over with another powder or powder bullet combo as I like to have 2 or 3 loads tested in case I cannot find certsin components.

[Variable]

Please don't load those. 8208 is a pretty fast powder, and everyone that has tried going above 28.5gr has seen a spike in pressure. 28.5gr under a 123gr is really where you want to stop.

Sage advice!

[motoxxx_ryder]

Please don't load those. 8208 is a pretty fast powder, and everyone that has tried going above 28.5gr has seen a spike in pressure. 28.5gr under a 123gr is really where you want to stop.

ok if its that consistent ill forgo the expanded ladder. That is the reason i was asking on here for some advice on it, i know there are tons of people who have been in my shoes and can save me some components and possiblly my face.

I ran from 25.5 to 28.5 in .5 increments and only 25.5 shot worth a darn. Ill probably run a true OCW this weekend see if i can find a better node between the .5s.

Thanks to all for the advice, just curious what powders you run for the 123 amax?

ETA: threw together my nest test. I used to run in .5 charges which works for the lapua at 90+ grs but i think its too large for the smaller calibers. below is my OCW test ill run shortly.

[NugginFutz]

My OCW for 123 Amax with IMR 8208XBR was run in 10 x .3 gr steps (1% of case volume) and ended at 29.0 grains, where I was definitely seeing primer flattening. Recently, I've been testing CFE223 with some promising groups at some decent velocities. I've not yet had time to go back and tune the CFE due to life's distractions.

I try to run all my OCW testing over a chronograph, which gives me the ability to both watch for changes/departures from the velocity curve, and gather ballistics information. At 200+ yards, movement over the chronograph is minimal and it takes virtually no extra time to build my position between shots.